Novel flux concentration stitched write head design for high data rate application

ABSTRACT

A flux concentrating stitched write head design for high data rate applications wherein said flux concentration is achieved by means of a non-magnetic step embedded into a portion of the lower magnetic pole just beneath the write gap layer. The design permits extremely short throat heights, which will be required by future high data rate applications.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates to the fabrication of a thin-film magnetichead. In particular, it relates to a method of fabricating a stitchedwriter portion of such a head that is suitable for high data-raterecording of magnetic information.

[0003] 2. Discussion of the Related Art

[0004] Thin film magnetic heads are used to record and retrieve datastored in the form of small magnetized regions on disks and tapes. Theseheads contain a read portion, which is typically a shielded magneticfield sensor of a giant magneto-resistive (GMR) type, and a writeportion, consisting of a magnetic pole and yoke structure inductivelyenergized by current carrying coils.

[0005] The need to record and retrieve data stored with increasing areadensities and at increasingly higher data rates has necessitated thedesign of very narrow write heads with high linear resolution. Thenarrow write head allows data to be stored in correspondingly narrowtracks. The high linear resolution, which is achieved by the formationof a thin write gap and a strong magnetic field, allows the storage ofmore data per unit length of track.

[0006] An important advance in the fabrication of write heads that helpto meet these stringent requirements is the so called “stitched writehead design.” This design embodies a simplified method of forming anarrow upper magnetic pole piece by joining or “stitching” together twoseparately deposited pole pieces, the upper pole tip and the upper poleyoke, along a pedestal formed from a portion of the upper pole tipphotoresist mask. In contrast to methods that form the upper pole pieceand yoke monolithically, the stitching process allows the narrow tipsection to be formed within a thinner photoresist mask, which is highlyadvantageous in the context of the fabrication process.

[0007] The performance of the stitched writer design and the advantagesinherent in the nature of its fabrication process can be furtherimproved by overcoming several deficiencies which limit itsapplicability to high data-rate recording. In particular, the stitchedwriter head as formed by the methods of the present art has a lengthythroat region along which the magnetic flux is diminished. Thus, inorder to maintain an acceptable flux level for recording at theair-bearing surface (ABS), the design requires a high saturation writingcurrent. This, in turn, causes side erasures and adversely affects dataalready written on adjacent disco areas.

[0008] Several methods have been advanced to improve the fluxcharacteristics of the stitched writer design and, indeed, to improvesuch other designs as have been suggested to meet the need for highrecording resolution. Chang et al. (U.S. Pat. No. 5,805,391) teach amethod for forming a write head with a recessed stitched yoke on aplanar portion of an insulating layer. The contour of said insulatinglayer minimizes the flux leakage between the yoke portion and the poletip portion stitched to it. Two inventions of Chen et al. (U.S. Pat. No.5,652,687 and U.S. Pat. No. 5,802,700) teach methods for forming a writehead having a U-shaped notch which opens out at the air-bearing surfaceand between whose ends is formed the upper pole tip. The structure soformed provides a parallel path for conducting the magnetic flux to saidpole tip, thereby allowing the proper flux concentration for writing innarrow trackwidths. The invention of Cole et al. (U.S. Pat. No.5,452,164) teaches a method of forming a pole tip structure that laysboth above and below the write gap and has a track width of less than 1micron. The symmetry of this arrangement supports good flux transferwith no leakage. The invention of Santini (U.S. Pat. No. 5,621,596)provides a method for improving the resolution of the photolithographyprocess that is used to define the shape of the pole tip. Specifically,the invention teaches a method of reducing light reflections in thephotolithography process by moving the point at which the pole yokeflares sufficiently far back from the position of the pole tip so thatreflections from the flare do not interfere with the definition of thepole tip.

[0009] An alternative approach to improving the flux characteristics ofthe stitched pole design involves concentrating the flux by improvingthe geometry of the junction between the upper pole tip and upper poleyoke. This is presently being achieved by a design (FIG. 1) thatincorporates a recessed upper pole yoke (FIG. 1 (10)) and a “step” (FIG.1 (12)) formed of non-magnetic material positioned in the rear undersideof the pole tip where it contacts the write gap layer. The stepeffectively channels the flux through a smaller area, thereby increasingits intensity across the write gap region (FIG. 1 (14)) and enhancingthe writing process. Although the use of the step provides a significantimprovement in the stitched head design, its placement in the pole tipwill ultimately prove to be disadvantageous as thinner pole tips andshorter throat heights are increasingly necessitated for high data-rateapplications. The present invention teaches a method for fabricating arecessed yoke, stitched head writer with the flux concentratingadvantages of the step formation, but without the disadvantages of thestep placement in the upper pole tip.

SUMMARY OF THE INVENTION

[0010] A first object of this invention is to fabricate a stitched pole,magnetic write head that is capable of recording magnetic data at highrates and increased densities.

[0011] A second object of this invention is to fabricate a stitched polemagnetic write head that has a lower saturation write current.

[0012] A third object of this invention is to fabricate a stitched polemagnetic write head with improved nonlinear transition shiftperformance.

[0013] A fourth object of this invention is to fabricate a stitched polemagnetic write head having improved overwrite performance.

[0014] A fifth object of this invention is to fabricate a stitched polemagnetic write head that significantly reduces the problem of sideerasure.

[0015] A sixth object of this invention is to fabricate a stitched polemagnetic write head with a reduced effective throat height and upperpole thickness.

[0016] These objects will be achieved by means of a novel modificationof the present stitched pole, stepped pole-piece fabrication process.The proposed modification is the removal of the step from the undersideof the upper pole piece and its effective repositioning in the form of a“recessed step,” a non-magnetic spacer embedded into an upper layer ofthe lower pole of the write head, said spacer thereby being placedbeneath the write gap layer of said write head. The flux concentratingregion so formed is less sensitive to the position of the upper polepiece, thereby allowing the formation of a shorter throat height as willbe required in future high data rate applications.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017]FIG. 1 is a schematic, cross-sectional view of a stitched polewrite head with a stepped upper pole piece designed according to theprior art.

[0018]FIG. 2a is the first of a series (FIGS. 2a-2 h) of schematiccross-sectional views of a stitched pole write head designed andfabricated according to the objects and methods of the presentinvention. FIG. 2a is a schematic view of a plated first part of S2,which is the upper shield of the read head portion of the read/writehead and also the lower pole piece of the write head portion. Said firstpart shall be designated S2A.

[0019]FIG. 2b is a schematic view of said plated first part, S2A, overwhich has now been plated a second part of S2, designated S2B. S2B hasbeen patterned with an opening which, when filled, will become therecessed, embedded step.

[0020]FIG. 2c is a schematic view of the fabrication in FIG. 2b, overwhich a dielectric layer has been formed.

[0021]FIG. 2d is a schematic view of the fabrication of FIG. 2csubsequent to the formation of an embedded step by the CMP processremoval of said dielectric layer.

[0022]FIG. 2e is a schematic view of the fabrication of FIG. 2dsubsequent to the formation of a write gap layer.

[0023]FIG. 2f is a schematic view of the fabrication of FIG. 2esubsequent to the formation of a front and rear portion of the upperpole piece, P2.

[0024]FIG. 2g is a schematic view of the fabrication of FIG. 2fsubsequent to the formation of a dielectric layer over said upper polepiece portions and its CMP process removal.

[0025]FIG. 2h is a schematic view of the completed stitched pole writerfabrication, showing the addition of the upper pole yoke, P3, insulatorsand induction coils. The fabrication in FIG. 2h, in accordance with thepresent invention, is to be contrasted to that of FIG. 1, fabricated inaccordance with the prior art.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0026] Referring first to FIG. 1, there is shown for comparison purposesonly a schematic sketch of a stitched pole writer designed in accordancewith the prior art and not using the methods of the present invention.The writer consists of a lower pole (1), which can also be the uppershield of a read head element positioned beneath the writer, a write gap(2), an upper pole piece with a front portion (3) and a rear portion (4)and an upper pole yoke that is stitched to the upper pole pieces (5) andmagnetically connects them. There is a flux concentrating non-magneticstep (6) formed on the bottom surface of the front portion of the upperpole piece. A coil (7) and insulating region (8) complete thefabrication.

[0027] Referring next to FIG. 2a, there is seen a schematiccross-sectional view of a plated first part of a lower pole piece (10)which forms the substrate for the fabrication of the present invention.Said lower pole piece, which is formed of (80/20) NiFe with a thicknessrange between 1.0 microns and 2.0 microns, can also serve as the uppershield of a read head portion of the read/write head, said read headportion being advantageously positioned beneath the write head of thepresent invention.

[0028] Referring next to FIG. 2b, there is shown the lower pole piece(10) of FIG. 2a, upon which has now been formed, by plating, a secondportion of the lower pole piece, which are formed together, in two parts(12), (14), with a gap (16) between them. Said second portion can becomposed of either (80/20) NiFe or CoNiFe, with a thickness rangebetween 1.0 microns and 3.0 microns and the gap can have a width rangingfrom 5.0 microns to 30 microns.

[0029] Referring next to FIG. 2c, there is shown the fabrication of FIG.2b, upon which has now been formed a dielectric layer (18), covering thetwo parts (12) and (14) and filling the gap (16) between them. Saiddielectric is composed of alumina and is formed, by RF diodessputtering, to a thickness range between 2.0 microns and 4.0 microns.

[0030] Referring next to FIG. 2d, there is shown the fabrication of FIG.2c wherein the dielectric layer referred to as (18) in FIG. 2c has beenremoved by a process of chemical mechanical polishing (CMP) forming,thereby, an imbedded step (20) within the gap (16).

[0031] Referring next to FIG. 2e, there is shown the fabrication of FIG.2d upon which has now been formed a write gap layer (22). The write gaplayer, which is formed of alumina with a thickness between 0.05 micronsand 0.5 microns, does not extend the full length of the second part ofthe second portion of the lower pole piece (14), leaving a space (24)for the subsequent formation of an upper pole piece that is in magneticcontact with said second part of said lower pole piece (14).

[0032] Referring now to FIG. 2f, there is shown the fabrication of FIG.2e upon which has been formed the two parts of the upper pole piece. Thefront part (26), which will be coplanar with the air-bearing surface andthe rear part (28) which is in contact with the lower pole piece (14).Said upper pole piece parts are composed of either Ni₄₅Fe₅₅ or CoNiFeand are formed to a thickness between 2.5 microns and 6.0 microns.

[0033] Referring now to FIG. 2g, there is shown the fabrication of FIG.2f upon which has been deposited, by RF diodes sputtering, an aluminadielectric layer of thickness between 4.0 microns and 9.0 microns. Saidlayer has then been partially removed by a method of chemical mechanicalpolishing (CMP) to leave behind a gapfilling layer (30) in the spacebetween the two parts of the upper pole piece (26), (28). The CMPprocess planarizes the top surface of the fabrication so that it issuitable for the subsequent fabrication of induction coils, insulatinglayers and an upper pole yoke as will be seen in the following figure.

[0034] Referring finally to FIG. 2h, there is shown a schematic drawingof the final stitched writer designed and fabricated according to theobjects and methods of the present invention. Induction coils (32), aninsulating layer composed of hard-baked resist (34) and an upper poleyoke (36) formed of Ni₄₅Fe₅₅ and Ni₈₀Fe₂₀ plated over the upper polepiece have been added to the fabrication of FIG. 2g. The upper pole yokeis recessed from the air-bearing surface (38) by an amount ranging from0.1 microns to 1.5 microns.

[0035] As is understood by a person skilled in the art, the preferredembodiment of the present invention is illustrative of the presentinvention rather than being limiting of the present invention. Revisionsand modifications may be made to methods, processes, materials,structures, shapes and dimensions through which is formed a fluxconcentration stitched write head design for high data rate application,while still providing a flux concentration stitched write head designfor high data rate application, formed in accord with the presentinvention as defined by the appended claims.

What is claimed is:
 1. A process for fabricating a flux concentratingstitched write head comprising: providing a substrate; forming on saidsubstrate a first part of a lower magnetic pole; forming on said firstpart a second part of a magnetic pole, said second part being formed intwo portions separated by a gap; forming a first dielectric layer oversaid second part such that said dielectric layer covers the top surfacesof both portions of the second part and conformally fills the gapbetween them; removing said dielectric layer from the surfaces of saidportions by a method of chemical mechanical polishing (CMP) but leavingsaid dielectric material to conformally fill the gap and to form,thereby, an embedded step; forming a write gap layer over said secondpart of the magnetic pole and embedded step such that said write gapdoes not extend fully to the rear of the second portion of said secondpart and, thereby leaves said second portion partially exposed;planarizing said write gap layer by a method of chemical mechanicalpolishing (CMP); forming an upper pole structure over said write gaplayer and said exposed portion of the second part of the magnetic pole,wherein said upper pole structure is formed in two separated portionswith the front portion being formed on the write gap layer and the rearportion being formed on the exposed lower magnetic pole part; forming asecond dielectric layer over said upper pole structure wherein saiddielectric layer covers both portions of the upper poles and conformallyfills the space between them; removing said dielectric layer from thecovered upper surfaces of said tipper pole structure by a method ofchemical mechanical polishing (CMP) but leaving said dielectric materialto fill the space between them; completing the fabrication by theformation of induction coils, insulating layers and an upper pole yokethat magnetically connects the front and rear portions of the upper poleformation and is recessed from the front surface of said upper poleformation.
 2. The method of claim 1 wherein the substrate is the uppershield of a read element.
 3. The method of claim 1 wherein the firstpart of the lower magnetic pole is formed by plating a layer offerromagnetic material over the substrate;
 4. The method of claim 3wherein the ferromagnetic material is Ni₈₀Fe₂₀ and is plated to athickness of between 1.0 microns and 2.0 microns.
 5. The method of claim1 wherein the ferromagnetic material forming each portion of the secondpart of the lower magnetic pole consists of either Ni₈₀Fe₂₀ or CoNiFeand is plated on to a thickness between 1.0 microns and 3.0 microns. 6.The method of claim 1 wherein the gap between the two portions of thesecond part of the lower magnetic pole has a width between 5.0 micronsand 30 microns.
 7. The method of claim 1 wherein the first dielectriclayer is a layer of alumina formed to a thickness of between 2.0 micronsand 4.0 microns.
 8. The method of claim 1 wherein the write gap layer isa layer of alumina formed to a thickness of between 0.05 microns and 0.5microns.
 9. The method of claim 1 wherein each of the two portions ofthe upper pole structure consist of either Ni₄₅Fe₅₅ or CoNiFe and areformed to a thickness of between 2.5 microns and 6.0 microns.
 10. Themethod of claim 1 wherein the second dielectric layer is a layer ofalumina formed to a thickness of between 4.0 microns and 9.0 microns.11. A flux concentrating stitched write head comprising: a substrate; afirst part of a lower magnetic pole formed on said substrate; a secondpart of a magnetic pole formed on said first part, said second partbeing formed in two portions separated by a gap that is conformallyfilled by a dielectric material to form, thereby, an embedded step; aplanarized write gap layer formed over said second part of the magneticpole and embedded step such that said write gap does not extend fully tothe rear of the second portion of said second part and, thereby, leavessaid second portion partially exposed; an upper magnetic pole pieceformed over said write gap layer and said exposed portion of the secondpart of the magnetic pole, wherein said upper magnetic pole piece isformed in two separated portions with the front portion being formed onthe write gap layer, the rear portion being formed on the exposed lowermagnetic pole part and the space between them conformally filled by adielectric material; a formation of induction coils, insulating layersand an upper pole yoke that magnetically connects the front and rearportions of the upper pole formation and is recessed from the frontsurface of said upper pole formation.
 12. The structure of claim 11wherein the substrate is the upper shield of a read element.
 13. Thestructure of claim 11 wherein the first lower pole part is formed of alayer of ferromagnetic material plated over the substrate;
 14. Thestructure of claim 13 wherein the ferromagnetic material is Ni₈₀Fe₂₀ andis plated to a thickness of between 1.0 microns and 2.0 microns.
 15. Thestructure of claim 11 wherein the ferromagnetic material forming eachportion of the second part of the lower magnetic pole consists of eitherNi₈₀Fe₂₀ or CoNiFe and is plated on to a thickness between 1.0 micronsand 3.0 microns.
 16. The structure of claim 11 wherein the gap betweenthe two portions of the second part of the lower magnetic pole has awidth between 5.0 microns and 30 microns.
 17. The structure of claim 11wherein the gap is conformally filled with a layer of alumina to form anembedded step.
 18. The structure of claim 11 wherein the write gap layeris a layer of alumina formed to a thickness of between 0.05 microns and0.5 microns.
 19. The structure of claim 11 wherein each of the twoportions of the upper magnetic pole piece consists of either Ni₄₅Fe₅₅ orCoNiFe and are formed to a thickness of between 2.5 microns and 6.0microns.
 20. The structure of claim 11 wherein the two portions of theupper magnetic pole piece are conformally filled by a layer of alumina.